A. Field
This invention relates to a method for avoiding multiple picks during the singling of sheet material as well as a corresponding apparatus for singling sheet material, in particular for bank note processing machines to which the bank notes to be processed are fed in stacks.
B. Related Art
Such bank note processing machines normally have for this purpose a pocket for receiving a bank-note stack. The bank notes are singled gradually by means of a singler from the upper side or underside of the stack. The singler has as a rule a singling gap which is formed on one side by a singling roller and on the other side by a retaining device, as a rule likewise a roller. A feeding system in the receiving pocket ensures that the bank notes to be singled are fed to the singling gap successively. The singling roller grasps by frictional engagement the furthest protruding one of the bank notes fed in this way. This should normally be the lowermost or uppermost bank note of the bank-note stack. The retaining roller on the opposite side of the singling gap normally stands still, but can in some cases also rotate in the opposite direction, thereby retaining the bank notes fed with the lowermost or uppermost bank note to the singling gap.
A problem of such apparatuses is the danger of overlapping double picks, multiple picks leading to continuous bands of bank notes, and blockage of the singler by wedging of bank notes in the singling gap. Such problems appear primarily when bank notes of mixed denomination with different formats are contained in the stack or when the bank notes are not carefully prestacked and the leading edges of the bank notes are spaced within the bank-note stack at very different distances from the singling gap. Such difficulties are to be observed especially with those receiving pockets that serve not only for inputting but also for outputting bank notes. With such pockets, bank notes not recognized by the bank note processing machine (so-called “rejects”) are restacked into a divided-off area of the pocket and frequently merely reinserted into the main pocket by an operator for a second run, or, e.g. if bank note processing is stopped, the already processed bank notes are restacked onto the not yet singled remaining stack and singled again in a second run. In such cases it happens that not the lowermost or uppermost bank note is grasped and singled during the singling process, but for example the third or fourth bank note, because its leading edge is much closer to the singling gap than the leading edges of the bank notes therebelow or thereabove. When this bank note protruding from the stack is grasped by the singling gap and pulled out of the bank-note stack, it pulls along adjacent bank notes, possibly resulting in the above-mentioned double picks, bank-note bands or a jam due to formation of a bank-note wedge in the singling gap. The retaining device retains the bank notes on one side of the bank note grasped by the singling gap. However, the bank notes pulled along on the other side of the grasped bank note, which originally should have been singled before the actually grasped bank note, are not influenced by the retaining device. They are then entrained with the actually grasped bank note as a double or multiple pick.
EP 0 942 887 B1 relates to an apparatus for singling sheet material which reduces the risk of multiple picks. In contrast to conventional apparatuses in which the feeding system for feeding the bank notes to the singling gap, which normally consists of feeding rollers or bands acting on the sheet stack from below or above, and the singling roller are coupled with each other synchronously via a common drive, different drives are provided according to the teaching of EP 0 942 887 B1 for the feeding system, on the one hand, and the singling roller, on the other hand. This permits the feeding system to be switched off after the singling roller has grasped a bank note, so that the singling roller completely takes over the picking function as of this moment. The feeding system thus in any case no longer has any supporting transport effect on those bank notes that are entrained with a singled bank note and should originally have been singled before it. However, EP 0 942 887 B1 does not relate to the concrete case of the double or multiple pick, which arises when another bank note of the bank-note stack is grasped instead of the bank note originally to be singled, and the bank note originally to be singled is entrained at the same time. Therefore, EP 0 942 887 B1 does not propose any concrete solution to this concrete problem. Furthermore, for reasons of space and cost it is not always possible to provide two separate drives or a corresponding gearing for separate control of the feeding system, on the one hand, and the singling roller, on the other hand.
EP 0 942 887 B1 also proposes feeding the bank notes by means of the feeding system against the singling roller standing still. This is also possible due to the separate drives. However, this as a rule does not obtain the result that adjacent bank notes are shifted relative to each other in such a way that the leading edge of a bank note to be singled is fed to the singling gap up to the level of a leading edge of another bank note protruding from the stack, or beyond it. Instead, it is also to be expected in this case that the protruding leading edge of the other bank note will be grasped by the singling gap first. In particular, this can additionally favor a wedging of bank notes in the singling gap under the stated circumstances.
EP 0 185 395 B1 describes an apparatus for singling bank notes wherein the bank-note stack to be singled is pushed with some momentum into the sheet store out of which the sheet material is then singled. In this singling apparatus, wherein the uppermost sheet of the sheet stack is always fed to the singling gap by means of compressed air and grasped by the singling roller by a vacuum, there was the problem of wedging in the singling gap upon insertion of the sheet stack into the sheet store due to the momentum with which the sheet stack slid through to the singling gap. To avoid this wedging, EP 0 185 395 B1 proposes a retaining apparatus with which a feeding gap between the sheet store and the singling gap is always closed when a new sheet stack is pushed into the sheet store. Before the onset of singling of the sheet material, the retaining device is withdrawn from the feeding gap so that the feed of the uppermost sheet to the singling gap can be effected by means of compressed air. The measure proposed in EP 0 185 395 B1 prevents wedging of sheet material in the singling gap, but does not ensure that the leading edge of the uppermost bank note to be singled is closest to the singling gap. If this is not the case and for example when the uppermost bank note is fed a bank note is entrained whose leading edge is closer to the singling gap, this note is grasped by the singling roller and entrains the bank note originally to be singled and any bank notes therebetween, which can lead to double or multiple picks and possibly to a jam due to wedging in the singling gap, which was originally to be prevented.
The problem of the present invention is therefore to avoid multiple picks during the singling of sheet material of a sheet stack.
This problem is solved by a method and apparatus having the features of the coordinated claims. Advantageous embodiments and developments of the invention are stated in dependent claims.
Accordingly, a further retaining device is provided. While the above-mentioned retaining roller or corresponding retaining device ensures that no sheet material is entrained with the singled sheet on the side of the singling gap facing away from the singling roller during singling by means of the singling roller, the further, separate retaining device acts on the fed sheet material before or in the singling gap from the opposite side of the singling gap. However, said further retaining device is only activated and therefore only acts on the sheet material fed to the singling gap after a sheet has been reliably grasped by the singler and has preferably already reached the downstream transport device. The singling roller and/or transport device then draws the sheet in question completely out of the sheet stack, while sheet material entrained between the singling roller (or equivalent singling device) and the sheet in question is retained by the further, separate retaining device.
According to a first embodiment of the invention, the further retaining device comprises friction elements which are urged against the sheet stack from above or from below depending on whether the sheet stack is being singled from above or from below. Entrained sheet material is thus braked and retained.
To retain the entrained sheet material even in the case of greatly overlapping sheets, it is advantageous to place the friction elements as close to the singling gap as possible. It is particularly advantageous if the retaining device acts on the sheet material to be retained in the singling gap or in a feeding gap between the singling gap and the sheet stack, by the singling gap or feeding gap being constricted, or—in the case of a regular pick—even completely closed, upon activation of the retaining element. The retaining device can have for example friction elements which are usually inserted into circumferential grooves of the singling roller so that in the non-activated state they neither hinder rotation of the singling roller nor act on the sheet material to be singled. Upon activation, the friction elements are moved out of the grooves, for example by means of a suitable lever mechanism, and constrict or close either the singling gap or a feeding gap before the singling gap (in the transport direction). For this purpose, the friction elements preferably have suitable friction linings, in particular made of rubber, on the side facing the sheet material to be contacted. Entrained sheet material is thus jammed to some extent in the singling gap or in the feeding gap.
The time coordination of the activation and deactivation of the retaining device with the transport of the bank notes to be singled is possible in different ways. The moment for activating the retaining element—that is the moment when the sheet to be singled has been reliably grasped by the singler or when it has preferably reliably reached a transport device downstream of the singler—can be determined for example by means of a light barrier by detecting when the leading edge of the picked bank note has reached the first transport nip of the transport device. The moment for deactivating the retaining device can be determined by means of a further light barrier by detecting for example when the trailing edge of the picked bank note has left the singling gap. The deactivation moment can also be determined indirectly with consideration of the transport speed of the transport system and the maximum length (e.g. 180 mm) of the sheet material to be singled.
Finally, the moments for activating and deactivating the retaining device can also be recognized solely or additionally with reference to the phase angle of the singling roller. The singling roller has friction segments at a defined place on its circumference which, when they come in contact with the leading edge of the sheet to be singled, grasp said leading edge and thus start the singling process. The retaining device is activated when the singling roller has rotated by such a phase angle that ensures that the leading edge of the sheet to be singled has been grasped by the transport device, and is deactivated again when the singling roller has rotated by a further phase angle that ensures that even a sheet with maximum length has left the singling gap.
Activation and deactivation of the retaining device can be effected by means of a separate actuator which reacts for example to the signals of the light barriers. However, activation and deactivation of the retaining device on the basis of certain phase angles of the singling roller also opens up the possibility of passive control by means of a cam coupled with the singling roller or by means of other gearing elements. The cam is then so disposed that it moves the retaining elements of the retaining device to their active position when the singling roller has reached a first defined phase angle, and to their inactive position when the singling roller traverses a second defined phase angle.
While the above-mentioned embodiments aim at proper processing of a double or multiple pick, the measure described hereinafter, which can be combined with the above-mentioned measures, aims at reducing the danger of this problematic case occurring from the start. The retaining device is disposed here, as explained above, so that it can close a feeding gap between the singling gap and the sheet stack. However, while this closing or constricting served in the hitherto explained embodiments to brake and thereby retain entrained sheet material, the retaining device can instead also be used to close the feeding gap and keep it closed when a sheet stack is inserted into the sheet store. To make sure that the uppermost or lowermost sheet to be singled is actually grasped by the singling roller first, the sheet in question is first preliminarily conveyed against the closed feeding gap by means of the feeding system. This process can last several singling cycles, but no singling occurs since the bank-note stack is separated mechanically from the singling roller by the retaining device.
Activation and deactivation of the retaining device can again be effected by means of a separate actuator. However, it is advantageous to use drive devices already contained in the system. In connection with bipartite pockets for receiving the sheet stack and for reoutputting rejects, as explained at the outset, a drive is for example already present for a movable intermediate plate which subdivides the pocket and on which the rejects are restacked. A preferred embodiment of the invention therefore provides for coupling the activation and deactivation of the retaining device with the motion of the intermediate plate.
A further idea of the present invention, which can also be used independently of the subject matter of the main claims, is the following.
If the sheet stack is placed on a support of the input pocket of the singler, it is normally pushed with the help of feed rollers integrated in the support toward the singling gap which is possibly still closed. The feed rollers are at the same time rotated by a given amount.
If, as described in DE 101 37 390 A1 from the applicant, a sensor is now provided which monitors during singling whether the next bank note to be singled is moving at the moment of singling, it can not only be detected whether the singling order has been mixed up. It is also possible to control the feed rollers individually in dependence on the signals of said sensor, i.e. to drive the feed rollers for different lengths of time depending on the actual position measured by the sensor, until the stack has been fed to the desired singling position.